In recent years, in response to the problem of global warming caused by petroleum-derived carbon dioxide, opportunities continue to arise throughout the world to overhaul social structures that are overdependent on fossil fuels. This trend is leading to increasingly active operation of “biorefineries” that make use of bioprocessing technology, for which research is accelerating throughout the world, but unfortunately under the current state of affairs no research results have yet been obtained for biosynthesis of aromatic compounds, although in light of the importance of aromatic compounds for the chemical industry, diligent efforts are being expended in research toward synthesis of aromatic polymers.
For example, PTL 1 discloses a technique relating to polymer synthesis using 4-aminocinnamic acid as a natural molecule, and reports that a high heat-proof polymer is obtained from 4-aminocinnamic acid.
Also, as disclosed in NPL 1, the metabolic pathway for biosynthesis of 4-aminophenylalanine via shikimic acid has been elucidated (see p. 2818, FIG. 1), but there has been no disclosure nor teaching of ammonia lyase functioning in an organism and converting 4-aminophenylalanine to 4-aminocinnamic acid.
NPL 2 is aimed at production of a super engineering plastic starting material by microorganic conversion of glucose and production of 4-aminocinnamic acid as a highly reactive amine-based aromatic compound from the starting material, and a synthesis method for 4-aminocinnamic acid is being investigated utilizing 4-aminophenylalanine as a starting material and ammonia lyase as a catalyst, as illustrated by the following scheme:

It has already been reported that 4-aminophenylalanine can be fermentatively produced using glucose as the starting material.
Ammonia lyase, a member of the lyase family, is a specific enzyme that cleaves carbon-nitrogen bonds, and it is known that phenylalanine ammonia lyase (hereunder also abbreviated as “PAL”) has the function of converting phenylalanine to cinnamic acid while tyrosine ammonia lyase has the function of converting tyrosine to 4-hydroxycinnamic acid.
NPL 2 reports that 0.12 g/L of 4-aminocinnamic acid was synthesized in resting cells reaction, using cells with Arabidopsis thaliana-derived ammonia lyase, but with such weak enzyme activity it is difficult for use as an industrial method. While Arabidopsis thaliana-derived ammonia lyase is one of the most commonly used ammonia lyases, it is not an enzyme suitable for 4-aminocinnamic acid synthesis from the viewpoint of enzyme activity that can be used for industrial production.
In addition, NPL 3 reports mutation analysis of PAL to improve the reaction rate on various substrates, but with 4-aminocinnamic acid, it is stated that it has an electron-withdrawing group on the benzene ring, and that conversion did not take place due to the presence of a positive mesomeric effect (see p. 930, right column, FIG. 2, p. 931, right column, Table II and p. 932, left column).
NPL 4, on the other hand, describes isolation of the gene for phenylalanine ammonia lyase of the yeast JN-1 Rhodotorula glutinis JN-1 (hereunder abbreviated as “RgPAL”), depositing of the yeast at CCTCC (China Center For Type Culture Collection) as deposit number M2011490, and creation of an optimum pH mutant by site-specific mutagenesis of the gene. Furthermore, since the Chinese Patent Application specification of which the authors of NPL 4 are the inventors (hereunder, PTL 2) was published on Apr. 24, 2013, the actual sequence of the RgPAL gene is publicly known. However, it is not disclosed that the enzyme can produce 4-aminocinnamic acid using 4-aminophenylalanine as the substrate.
Thus, there has not yet been established a production method that allows 4-aminocinnamic acid to be industrially mass-produced by an enzyme process, or an enzyme suited for such a method, and development thereof is strongly desired.